1. Field of the Invention
The present invention relates to a non-linear signal receiver, and more particularly, to a non-linear signal receiver for stably restoring the sampling time of a signal reproduced from a data storage device, taking in consideration non-linear distortion of the signal.
2. Description of the Related Art
In general, non-linearity becomes a serious problem as recording density increases in digital magnetic recording media such as a hard disk drive (HDD). Non-linearity is generated due to interactions between adjacent transitions. A demagnetization field of a previously recorded transition shifts the position of a subsequently recorded transition and increases the width between transitions. The adjacent transitions operate to erase each other. As a result, the amplitude of a reproduced signal is reduced. Such phenomenons are known as a non-linear transition shift (NLTS), a transition broadening, and a partial erasure. Such non-linear distortion adversely affects a series of processes for detecting data from the reproduced signal, and makes it difficult to search an accurate phase of the signal. In case that such non-linear distortion characteristic is not considered, timing jitter and bias become serious.
To solve the problems, U.S. Pat. No. 4,890,299 discloses a method for correcting the sampling phase of a partial-response (PR) signal without causing hangups in which the sampling phase correction is interrupted for a predetermined period of time. However, the method is effective on only linear signals. That is, it is difficult to apply this method to a signal having non-linear distortion. Also, other conventional methods for phase compensation have been based on the assumption that a signal is linear. Thus, these methods cannot be used for a signal having serious non-linear distortion.
It is an object of the present invention to provide a non-linear signal receiver for modeling signals sampled in consideration of past, current and future bit data, and correcting sampling-timing phase from the phase gradient among the sampled signals.
To achieve the object of the present invention, there is provided a non-linear signal receiver for detecting an original data ak from an input signal r(t) which is a binary data stream input through a channel or reproduced from data recorded on a storing device, the receiver comprising: an analog-to-digital converter (ADC) for sampling the input value according to sampling timing phases, and converting the sampled data into a digital signal rk; a modeling portion including 2N+1 taps Pn (n=xe2x88x92N, . . . , 0, . . . , N) each for selecting one of 2xcfx84+xcexd tap values according to each pattern pn (bkxe2x88x92n+xcexd:kxe2x88x92n+l, bkxe2x88x92nxe2x88x921:kxe2x88x92nxe2x88x92xcfx84) of absolute values of the data transitions future xcexd bits and past xcfx84 bits, for estimating the channel characteristics of the sampled signal from the selected tap value and the data transition value; a timing recovery portion for controlling the sampling timing phase of the analog-to-digital converter using a phase gradient which is the difference between values of respective taps positioned symmetrically around the tap P0 of the modeling portion; an equalizer for compensating for the deteriorated characteristics of the output value of the analog-to-digital converter; and a detector for converting the output of the equalizer to a digital value, to detect the original signal.